Brains in the city: Neurobiological effects of urbanization

Abstract

With a majority of humans now living in cities, strategic research is necessary to elucidate the impact of this evolutionarily unfamiliar habitat on neural functions and well-being. In this review, both rodent and human models are considered in the evaluation of the changing physical and social landscapes associated with urban dwellings. Animal models assessing increased exposure to artificial physical elements characteristic of urban settings, as well as exposure to unnatural sources of light for extended durations, are reviewed. In both cases, increased biomarkers of mental illnesses such as major depression have been observed. Additionally, applied human research emphasizing the emotional impact of environmental threats associated with urban habitats is considered. Subjects evaluated in an inner-city hospital reveal the impact of combined specific genetic vulnerabilities and heightened stress responses in the expression of posttraumatic stress disorder. Finally, algorithm-based models of cities have been developed utilizing population-level analyses to identify risk factors for psychiatric illness. Although complex, the use of multiple research approaches, as described herein, results in an enhanced understanding of urbanization and its far-reaching effects--confirming the importance of continued research directed toward the identification of putative risk factors associated with psychiatric illness in urban settings.

Keywords: Agent-based models; Animal models; Collective efficacy; Depression; Intercity violence; Light pollution; Natural environment; PTSD; Psychiatric illness; Self-efficacy; Socioeconomic disadvantage; Urbanization.

Figure 1

Examples of natural-enriched (left) and artificial-enriched (right) environments. Groups of 10 animals were housed in these environments in which an equal number of objects, with similar functions, were presented to the animals.

Figure 2

Artificial light at night as seen from space. Images are composites acquired by the NASA Suomi NPP satellite in 2012. A TIFF file is available at: earth_lights_4800.tif

Figure 3

Brain activation to fearful vs. neutral faces is higher in A) Subjects with PTSD compared to trauma controls, and B) ACYAP1R1 CC genotype compared to G allele carriers.

Figure 4. Agent locations in a grid of neighborhoods, with Agents (a) segregated in neighborhoods by race and Income, or (b) assigned random locations

Note. Each racial/ethnic group is represented by a different shade of gray (black: other non-Hispanic; medium gray: Hispanic; light gray: Black non-Hispanic; lightest gray: White non-Hispanic). Darker circles reflect higher income levels within each racial/ethnic group. Figure taken from: (Cerda et al., 2014). Figure copyright: American Public Health Association.